Carburizing box



Marc 1933. H, HARRiS 2,034,18

CARBURIZING B Patented Mar. 17, 1936 UNTED STATES PATENT oFFicE 3Claims.

This invention relates to carburizing boxes and is an improvement on theinvention of my Patent No. 1,882,580.

It is an object of my invention to provide a carburizing box which willstand up better and longer under the severe usage which such bo-xesreceive.

It is a further object of my invention to provide a carburizing boxwhich will have a longer service life in proportion to the diiiicultyand expense of making same.

Other objects will appear in the course of this speciiication.

When carburizing boxes are to be used in heat treating furnaces, metalarticles to be carburized are placed in the boxes, together with acarburizing agent such as bone dust. Trays are placed over the boxes,the boxes with their trays are then usually inverted, and in thisposition subjected to heat suppliedfrom beneath in a heat treatingfurnace.

The boxes must stand up under rough handling, extremely hightemperatures, sudden changes in temperature, and the pressure of a heavyload of contents while softened by heat, all with attendant warping andbuckling, producing cracks in the course of time and. ultimatelybreaking the box down.

As a result, if the boxes were not made so as to have great durabilityunder such treatment they would have to be replaced constantly at greatexpense, and it becomes a problem of some nicety and importance todevise a box having the longest life in proportion to the cost ofproducing same.

I have found that the ordinary rectilinear box breaks down first alongthe open edges at about the centers of the longer sides, this principallocus of failure being indicated by arrow l in Fig. 3 of the drawing.

While the form shown in my prior patent above referred to is an advanceover former practice, I have now devised a construction which is animprovement thereon, greatly increasing the life of carburizing boxeswithout greatly increasing the amount of high grade alloy required, andwhich at the same time is easier to make.

In the drawing, Fig. 1 is a perspective View of a box constructed inaccordance with my invention;

Fig. 2 is a plan view thereof; and

Fig. 3 is a side view thereof with a portion broken away.

The carburizing box of this invention consists of three sections A, Band C, united together as at i l and I2, preferably by welding withwelding stick material. The end sections A and C are preferably formedof relatively inexpensive metal, such as low-grade iron-nickel-chromiumalloy, preferably cast. The center section or gusset B is formed, castor in sheet, of a high grade heat resistant ductile alloy, such asQ-alloy which has a high nickel chromium content. This gusset B islocated midway of the length of the box, extending down one side, acrossthe bottom, and up the other side. The portion in the bottom isrelatively narrow, being shown for example as about one-iifth the lengthof the box. As the gusset strip starts up each side it flares out, untilat the top edge it is shown for example as comprising about half of thelength ol the box.

A thickened edge or bead I8 is formed along the top edge of all thesections.

Making the end and center parts as separate sections provides anaccommodating and equaliZing-of-strain effect, which is increased bymaking the center section of higher grade alloy better adapted towithstand and absorb strains.

By this construction the part of the box at the principal locus offailure is strengthened by provision thereat of an adequate width oi'highly resistant flexible material to take up strains, and at the sametime a continuous strip of this material capable of absorbing andwithstanding strains is provided all the way around the center part ofthe box to take up the strains oi the box as a whole with a minimum ofthe expensive alloy material.

With this construction the end sections A and C are easier to cast, orshould they be made oi sheet material are easier to form therefrom.These sections are generally cast about a solid core. Since with thepresent construction each end piece approaches more nearly a simplesaucer shape rather than a deep cup shape it is easier to cast, hasfewer casting strains, and can be cast thinner. The bead I3 around thetop edge becomes feasible with this shape end section, because it is nowpossible to cast the main body of the end section no thicker thannecessary, while the top edge is left thicker to meet localized strains.

It will be seen that by this invention I have achieved a carburizing boxof longer life with minimum expense and weight. While I have shown onespecific form to illustrate the invention, it will be apparent thatvariations thereof may be made within the spirit of the invention,

and hence I wish to be limited only by the scope of the appended claims.

I claim:

1. A metallic receptacle for use in heat treating furnaces comprising ashell having a rectangular open top', the top edges being formed thickerthan the Walls of the box to provide a reinforcing bead, and a gussetset in and extending around the shell -transverse toy its longerdimension, said gusset at the edges of the open top comprisingsubstantially the central half of the side walls, and at the bottoms ofthe side walls and across ber widens gradually and smoothly from itsnar- 10 row bottom portion to its wide side edge portions.

HENRY H. HARRIS.

